a filter or an electric dust collector has conventionally been used for removing dust contained in exhaust gas discharged from an incinerator or the like. When a filter is used, it is necessary to periodically conduct back wash because the filter is clogged, and there is a drawback of an increased size of the apparatus in order to conduct a continuous treatment. When an electric dust collector is used, there is a drawback of causing re-dispersion phenomenon when fine powdery dust having low electric resistance is collected, thereby inhibiting dust collection efficiency from rising. To make up for the drawbacks, a dust collector where electrostatic dust collection and silent discharge are combined with each other is considered.
As a dust-collecting electrode (sometimes referred to as a “discharge electrode”) used for a dust collector where an electrostatic dust collection and silent discharge are combined with each other, it is noted that a dust-collecting electrode is provided with two unit electrodes where both ends of the unit electrodes are fixed and a dielectric body disposed between the unit electrodes. In a dust-collecting electrode constituted in such a manner, silent discharge is generated between the unit electrodes by applying a high voltage alternating current or periodic pulse voltage between the unit electrodes to form a discharge field, where an active species, a radical, and an ion are generated to promote reaction and decomposition of gas. In addition, since an electric field is generated between the unit electrodes at this time, when fine powdery dust is passed through the space between two unit electrodes, the fine powdery dust is drawn onto one of the two unit electrodes. Thus, since the aforementioned dust-collecting electrode can draw fine powdery dust onto a unit electrode constituting a dust-collecting electrode and can directly decompose the fine powdery dust by the silent discharge between the dust-collecting electrodes, re-dispersion of the fine powdery dust can be avoided.
In addition, a secondary effect of treating harmful components, for example, highly toxic dioxin such as polychlorinated dibenzo-p-dioxin (PCDD) and polychlorinated dibenzofuran (PCDF) contained in the gas besides fine powdery dust such as dust can be expected by passing the gas discharged from various kinds of incinerators and the like through the aforementioned discharge field, and an electrostatic dust collector provided with such a discharge electrode has been disclosed (see, e.g., non-Patent Document 1).
Such a discharge electrode is exemplified, as shown in FIG. 7, by a discharge electrode 31 provided with a dielectric body 32 constituted by a ceramic and the like, a conductive layer 34 disposed inside the dielectric body 32, and an electric wiring 33.
A discharge electrode 31 shown in FIG. 7 can cause discharge in the vicinity of the surface of the dielectric body 32 by applying voltage between the conductive layer 34 and the electric wiring 33. The state of the discharge generated in the vicinity of the surface of the dielectric body 32 is called creeping discharge, and fine powdery dust can be decomposed by passing the fine powdery dust in the creeping discharge.
Non-Patent Document 1: “Plasma Gas Phase Reaction Engineering” by Shinriki Teii and Shigeru Ono, published by Uchida Rokakuho on Apr. 28, 2004; Page 107